Airplane-propeller gear



March 31 1931. c JENKINS 1,798,740

AIRPLANE PROPELLER GEAR Filed Feb. 19, 1929 Patented Mar. 31, 1931 NITED STATES PATENT OFFICE FRANCIS JENKINS, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOIR T AIRPLANE-PROPELLER GEAR Application filed February 19, 1929. Serial No. 341,152.

This invention relates to airplane propeller gear, and has for its principal object means for adjusting the pitch of the blades during flight.

it it is well known that the pitch of the blade of a flying machine propeller, to be most effective should be set with a diiierent pitch in tlight from that best adapted to getting off the ground.

This has been well known for a longtime, but simple, rugged, dependable and practical means to this end has not heretofore been available.

Any other than an absolutely dependable lit service is a source of danger to pilot and passengers, for the plane cannot come to rest in the air as a motor boat can on the water, because of propeller fault. The plane must come to earth, and no unreliable propeller W gear can be tolerated.

Again the angle of pitch of the blades must be exactly the right angle. There must, therefore, be no slack or springiness in gear design or material if efficiency is to be assured.

Ruggedness as much as accuracy of blade setting is, therefore, absolutely essential to insure that degree of safety and efficiency in flight demanded in modern aircraft.

9 The problem, therefore, is more than .just a design and structure which would pass in other transportation vehicles. Therein lies the importance of the apparatus disclosed and claimed in this specification.

The present device consists of a propeller having angularly rotatable blades, and means including a rigidly-held quadrant-rack with accurately located slots therein for setting and holding the pitch of the blade with a high degree of'accuracy with a different setting in flight.

With this and other objects in view the invention consists of the novel combinations of parts herein described, illustrated in thedrawings, and particularly pointed out in the claim.

In the drawings, Figure 1 illustrates the propeller gear; Figure 2 the slotted quadrant for setting and accurately holding the pitch of the propeller blades; and Figure 3 a new of the blade lever-arm.

In the Figures A is the propeller hub; B and B the propeller blades which may rotate in the hub to set the pitch; C the lever by which said pitch setting is attained; D a collar concentric with the hub and movable toward and from the blade; E a rod connecting the collar and the blade lever; F a ring lying in a groove in the movable collar; G is a stiff rod welded or otherwise fastened to the ring; the opposite end of the rod being attached to a hand-lever H. The free end of the lever has a latch J thereon which detachably engages with a notched quadrant K.

This quadrant is stifiiy' braced to'the engine frame N by rigid connection L; and the lower, or fulcrum end, of the lever by the brace M. l

The operation of the device is as follows The enginebeing warmed up, and all preparations complete for the take-oil, the propeller-angle lever-arm latch J is placed in the middle slot of quadrant K. This 'ves (1) a less angle setting to the pitch 0 the blades; (2) a higher rotation of the engine; and, therefore, (3) more power and a quicker take-off.

The resultant quicker take-0E makes for safety, for the pilot gets the plane to a safe elevation much quicker, and in a shorter ground-run.

Having reached a preferred flying level, the pilot now sets the latch in. the adjacent,

forward notch of the quadrant, and the engine slows down by reason of the increased pitch of the blade setting while the plane still maintains the same flying speed.

The accuracy of these settings-is extremely important. It has, therefore, been found necessary to carry forward to the engine frame rigid reach-rods, L from the quadrant, and M from the fulcrum of the lever H. The stiffness of the latter rod, M, is the more important of the two, for obviously, with the rod G attached low down on the lever H, any displacement of fulcrum of the lever, even a slight displacement, would died the blade pitch-setting far more than a similar displacement of quadrant K.

What is claimed is In an airplane propeller gear having adjustable pitch blades, a lever for adjusting the blades, an engine frame, a quadrant for engaging the lever and on which the lever is fulcrumed, an upper inclined brace extend: ing from the top of the quadrant to the engine frame, and a lower substantially horizontal brace extending from the fulcrum of the lever to the engine frame, said braces converging toward the engine frame and forming a rigid connection between the quadrant and the engine framefor firmly holding-the lever in position when the latter is adjusted.

In testimony whereof I have afiixed my signature.

CHARLES FRANCIS JENKINS. 

